Pulse oximetry is a widely accepted noninvasive procedure for measuring the oxygen saturation level of arterial blood, an indicator of a person's oxygen supply. Early detection of low blood oxygen level is critical in the medical field, for example in critical care and surgical applications, because an insufficient supply of oxygen can result in brain damage and death in a matter of minutes. A pulse oximetry system consists of a sensor applied to a patient, a monitor, and a patient cable connecting the sensor and the monitor. The sensor is attached to a tissue site, such as an adult patient's finger. The sensor has an emitter configured with both red and infrared LEDs that, for finger attachment, project light through the fingernail and into the blood vessels and capillaries underneath. A detector is positioned at the finger tip opposite the fingernail so as to detect the LED emitted light as it emerges from the finger tissues. In general, the emitter is adapted to transmit optical radiation of at least two wavelengths into a tissue site, and the detector is adapted to receive optical radiation from the emitter after absorption by pulsatile blood flowing within the tissue site.